1. Field of the Invention
The present invention relates to a hard disk drive, and more particularly, to a voice coil motor coupling structure of a hard disk drive for coupling a voice coil motor which pivots an actuator to a base plate.
2. Description of the Related Art
Hard disk drives (HDDs) are auxiliary memory devices for a computer which record and reproduce data on a magnetic disk using a magnetic head.
FIG. 1 is a plan view illustrating a conventional hard disk drive. FIG. 2 is a perspective view illustrating a conventional actuator and a conventional voice coil motor.
Referring to FIGS. 1 and 2, a conventional hard disk drive comprises a magnetic disk (hard disk) 20 which is a recording medium where data is recorded, a spindle motor 30 installed on a base plate 10 and rotating the magnetic disk 20, and an actuator 40 having a magnetic head 41 to record data on the magnetic disk 20 and reproduce the data from the disk 20.
In general, one or more magnetic disks 20 separated at a predetermined distance from each other are installed to be rotated by the spindle motor 30. On the disk 20, a parking zone 21 is provided at the inner circumferential side of the disk 20 and a data zone 22 where a magnetic signal is recorded is provided outside the parking zone 21. A slider 42 is disposed in the parking zone 21 when the power is turned off.
The actuator 40 is installed on the base plate 10 and pivots around a pivot shaft 47 provided on the base plate 10. The actuator 40 has an arm 46 in which a pivot hole 48 is formed in the middle portion thereof so that the actuator 40 can be coupled to the pivot shaft 47. A suspension 44 installed at one end portion of the arm is elastically supporting the slider 42 having the magnetic head 41 toward a surface of the magnetic disk 20.
The actuator 40 pivots by a voice coil motor (VCM) 50. The VCM 50 has a coil 56 coupled to the other end portion of the arm 46. A lower yoke 51 is fixedly installed on the base plate 10 under the coil 56 separated by a predetermined distance. An upper yoke 52 is installed above the coil 56 and coupled to the lower yoke 51 by a screw 59. Magnets 53 and 54 are attached to the upper surface of the lower yoke 51 and the lower surface of the upper yoke 52, respectively. The respective magnets 53 and 54 are separated a predetermined distance from the coil 56.
An actuator locking apparatus is provided for locking the actuator 40 when the slider 42 is disposed in the parking zone 21 of the magnetic disk 20. The actuator locking apparatus comprises a metal piece 63 installed at an end portion of the arm 46, a bending portion 66 extending from an edge of the upper yoke 52 and bent downward and contacting with the upper surface of the lower yoke 51, and a slot 67 formed in the bending portion 66.
FIG. 3 is a side view illustrating a conventional voice coil motor coupling structure. FIG. 4 is a perspective view illustrating a method of coupling the conventional voice coil motor on the base plate. In FIGS. 1-4, the same reference numerals indicate the same elements having the same functions.
Referring to FIGS. 3 and 4, a boss 14 protrudes from the upper surface of the base plate 10. The boss 14 is inserted in a boss insertion hole 57 which is provided at one end portion of the lower yoke 51. A screw insertion hole 58 into which a screw 59 is inserted is formed in the other end portion of the lower yoke 51. Additional screw insertion holes 56a and 56b into which screws 59 are inserted are formed at both end portions of the upper yoke 52.
In the above coupling structure, in order to couple the voice coil motor 50 to the base plate 10 the lower yoke 51 and the upper yoke 52 are firmly coupled by a magnetic force of the magnets 53 and 54. While the lower yoke 51 and the upper yoke 52 are coupled, the boss 14 formed on the base plate 10 is inserted into the boss insertion hole 57 provided at one end portion of the lower yoke 51. Then, the lower yoke 51 and the upper yoke 52 are rotated around the boss 14 to match the screw insertion holes 58 and 56b to a screw coupling hole 12 formed in the base plate 10. The coil 56 coupled to a rear end portion of the arm 46 is inserted between the two magnets 53 and 54. The lower yoke 51 and the upper yoke 52 can be rotated since the upper surface of the base plate 10 is flat. Then screws 59 are inserted into the screw insertion holes 56a, 56b, and 58 and coupled to the screw coupling holes 12, so that the lower yoke 51 and the upper yoke 52 are fixedly installed on the base plate 10.
In the conventional hard disk drives, a plurality of disks are installed to increase a data storage capacity. However, with a rapid increase in surface recording density of a disk, one or two disks can store a sufficient amount of data. In particular, hard disk drives using a single disk in which data is recorded on only one side have been developed. Since only one magnetic head and one arm is needed, hard disk drives can be made narrower. In the conventional hard disk drives, a voice coil motor in which magnets are provided at the upper and lower sides of a coil is mainly used. However, in a case of an actuator having only one arm for a single disk, a voice coil motor requiring a single magnet installed only on one of the upper or lower sides of the coil may be desired. Therefore, hard disk drives can be made narrower.
The type of the base plate has changed from a conventional flat type to a bowl type. When the base plate is made into a bowl type, since a flat cover plate is coupled to the base plate by pressing, the cost for manufacturing may be reduced compared to that of the conventional bowl type cover plate manufactured by aluminum die casting. Since the lower yoke and the upper yoke of the voice coil motor may interfere with a protruding side wall of the interior of the bowl type base plate, the voice coil motor cannot be assembled in a state in which the lower yoke and the upper yoke of the voice coil motor are first coupled together. Thus, after the lower yoke is assembled to the base plate, the actuator arm is assembled so that the rear end portion of the actuator arm to which the coil is coupled is disposed above the lower yoke. Then, the upper yoke is coupled to the lower yoke. Since the lower yoke is not first stably fixed to the base plate, when the upper yoke is coupled to the lower yoke, the lower yoke is moved horizontally and vertically by the magnetic force of the magnet attached to the lower surface of the upper yoke, which makes it difficult to couple the voice coil motor. Therefore, a new voice coil motor coupling structure is needed in the hard disk drive having the above structure.